Suspension

ABSTRACT

A rear axle suspension for a highway truck that includes a pair of trailing arms suspended below a frame by a pair of hanger brackets. The hanger brackets define a pivot axis for the trailing arms. A supplemental axle locating member is attached to the axle and includes an extension member that in engageable with a bracket held by the frame. The hanger brackets are laterally compliant and each comprise an inner and outer plate, one of which is bent outwardly to define a gap within which an associated trailing arm is mounted. A moment canceling member extends between the hanger brackets and resists outward bending of the brackets. A height control valve is operated by an operating rod having an axis that passes through, or in close proximity, to the roll center of the vehicle in order to reduce ride height errors.

TECHNICAL FIELD

[0001] The present application relates generally to suspensions and, inparticular, to a rear, trailing arm type suspension.

BACKGROUND ART

[0002] Many vehicles such as highway trucks include trailing arm typesuspensions which support a rear axle and define its path of movementwith respect to the vehicle frame. In some current highway truckdesigns, each trailing arm is constructed of spring steel and maycomprise one or more “leaves.” The term “leaves” is used because atleast some of the trailing arms being used by truck manufacturers arebeing made by leaf spring manufacturers from materials and inconfigurations that are or were used in “leaf” springs. In conventionaldesigns of this type of suspensions, outboard ends of the axle aresecured to respective trailing arms and, in effect, the arms support andlocate the axle with respect-to the vehicle frame.

[0003] In some current suspension designs, the leading end of thetrailing arm is suspended below its associated frame member by a hangerbracket. These hanger brackets are typically rigid cast components, andsubstantially resist bending in response to torsional stresses placed onthe bracket by the trailing arm. These brackets typically dependdownwardly only a short distance with respect to the frame. As a result,the distance between the trailing arm pivot axis and ground can besubstantial. The distance of the pivot axis above ground level canaffect the ride quality of the vehicle. It is usually desirable to lowerthe pivot axis when possible. However, simply elongating an existinghanger bracket design in order to lower the trailing arm pivot axis,does not provide satisfactory performance.

DISCLOSURE OF INVENTION

[0004] The present invention provides a new and improved suspension thatit suitable as a rear suspension for a trailing arm type suspension,such as those found in highway trucks.

[0005] According to one feature of the invention, the suspensionincludes a trailing arm pivotally connected to a frame member by ahanger bracket. A rear axle is attached to the trailing arm. Asupplemental axle locating member is provided which supplementallylocates the axle with respect to the frame. In the illustratedembodiment, the locating member is attached to the axle and includes anupwardly extending finger that is engageable with a bracket secured tothe frame. The bracket includes abutment surfaces slidably engageablewith the extension finger.

[0006] According to another feature of the invention, a rear suspensionis disclosed that includes laterally compliant hanger brackets whichdefine a pivot axis for the trailing arms that is substantially lowerthan conventional designs. Each hanger bracket comprises a pair ofcompliant steel plates. Top portions of the plates are connected to anassociated frame rail. In the illustrated embodiment, an inner plate issubstantially planar, whereas an outer plate is bent outwardly and thendownwardly to define a planar mounting section that is parallel to theplane of the inner plate. A gap is defined between the plate withinwhich the leading end of the trailing arm is secured. The position ofthe trailing arm with respect to the hanger is adjustable in order toprecisely locate the axle with respect to the frame. Speciallyconfigured spacer and mounting components are utilized to provideclamping forces that resist relative movement between the hanger bracketand trailing arm after an adjustment is made.

[0007] According to another feature of the invention, each trailing armincludes a spring seat to which an air spring is attached. The line ofaction for the air spring is located such that it passes through theframe sheer center of its associated frame rail. In addition, thelocation of the air spring takes advantage of clearance provided by theinner periphery of an associated wheel. As a result, the air springs aremounted nearer the outboard ends of the axle, as compared to moreconventional designs.

[0008] According to another feature of the invention, a shock bracket isprovided that includes ears that provide some protection for shock inthe event of impact.

[0009] According to another feature of the invention, an air valveoperating configuration is provided which reduces ride height errors. Inparticular, an air spring control valve is attached to a frame memberand includes a control lever. An operating rod couples the lever to theaxle. In the illustrated embodiment, the operating rod is connected to amounting member extending from a shock mount. The axis of the operatingrod is configured such that it passes through or in close proximity tothe roll center of the vehicle. As a result, rolling of the vehicle bodywhen rounding a curve eliminates or substantially reduces ride heighterrors.

[0010] Additional features of the invention will become apparent and afuller understanding obtained by reading the following detaileddescription made in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0011]FIG. 1 is a side elevational view of a rear suspension for a dualaxle vehicle, such as a Class 8 highway truck;

[0012]FIG. 2 is a fragmentary perspective view of the suspension shownin FIG. 1;

[0013]FIG. 3 is a perspective view of a supplemental axle locatingmember forming part of the present invention;

[0014]FIG. 3A is a sectional view of the supplemental axle locatingmember;

[0015]FIG. 4 is a fragmentary, front view of a trailing arm mountingforming part of the present invention;

[0016]FIG. 5 is a side view of one of the plates that comprise atrailing arm hanger bracket constructed in accordance with a preferredembodiment of the invention;

[0017]FIG. 6 is a side elevational view of another plate that forms partof the trailing arm hanger bracket constructed in accordance with thepreferred embodiment of the invention;

[0018]FIG. 6A is an end view of the plate shown in FIG. 6;

[0019]FIG. 7 is a fragmentary, front view of the hanger bracket andtrailing arm mounting;

[0020]FIG. 8 is a fragmentary, bottom view of the suspension shown inFIG. 2;

[0021]FIG. 9 is a fragmentary, rear view of a rear suspension thatincludes a height control system.

[0022]FIG. 10 is a sectional view of a trailing arm mounting constructedin accordance with the present invention as seen from the planeindicated by the line 10-10, with the components shown in a positionbefore final torquing of a securement fastener is made; and,

[0023]FIG. 11 illustrates the trailing arm mounting shown in FIG. 10after the securement fastener is torqued.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024]FIG. 1 illustrates a rear suspension of a tractor unit of ahighway truck constructed in accordance with the preferred embodiment ofthe invention. The illustrated suspension is intended for use with atractor unit having dual rear axles, indicated generally by thereference characters A1, A2. However, the invention can be used with atractor unit having a single rear axle.

[0025] For purposes of explanation, the suspension components for theleading rear axle A1 will be described and are illustrated in FIG. 2. Itshould be understood, however, that the inventive features can be usedon either or both of the rear axle suspensions.

[0026] The suspension illustrated in FIG. 2 is best characterized as atrailing arm, pneumatic or air suspension. In particular, the suspensionincludes a trailing arm 10, the forward end of which is held by atrailing arm hanger bracket 14. As seen best in FIG. 2, the hangerbracket 14 is mounted to and depends downwardly from the side of a framerail or frame member 16 and defines a pivot axis 19 for the trailing arm10. Like components (not shown) are mounted to an opposite frame member18.

[0027] Referring also to FIG. 8, the opposite end (i.e. trailing end 20)of the trailing arm 10 defines a seat 21 for a spring unit 22. In theillustrated embodiment, the spring unit comprises a conventionalpneumatic cushion filled with air at a predetermined pressure. The airpressure acts as an air spring and may be varied to change the springrate. A rearwardly extending bracket 24 connects the trailing end 20 ofthe trailing arm 10 to a shock absorber 26. In effect, the shockabsorber 26 interconnects the trailing end 20 of the trailing arm 10 tothe frame 16. The upper half or “fixed” end of the shock absorber 26 issecured to a bracket 28 that is attached to the frame 16. The upper partof the shock, preferably includes an elastomeric bushing 30. A securingbolt 32 extends through the bracket 28 and through the bushing 30 tosecure the upper part of the shock 26 to the frame 16. The bushing 30does allow some movement in the upper part of the shock to accommodatemovement in the lower part of the shock as the trailing arm 10 rotatesclockwise or counterclockwise about its pivot 19. The lower part of theshock 26 is pivotally connected to the extension bracket 24.

[0028] In the preferred embodiment, the trailing arm 10 is formed fromspring steel and, in effect, acts as a single leaf-type spring. Springsteel is used as the trailing arm because its elasticity does allow somebending movement and, as a result, reduces stress levels at the variousmounting points including the mounting location for the vehicle axle.

[0029] According to one feature of the invention, a supplemental axlelocating device 40 is provided which acts to inhibit fore and aftmovement in the axle housing should a failure in the trailing arm occur.In prior art suspensions, multiple spring leaves are used to define thetrailing arm.

[0030] In the type of suspension illustrated in FIG. 1, the position ofthe axle housing is determined by its attachment to the trailing arm 10.During use, the axle moves upwardly and downwardly with respect to theframe 16, to accommodate road irregularities. Its path of movement isdefined by the trailing arm 10.

[0031] In the illustrated construction, an outboard end of an axlehousing is held to the trailing arm 10 by a pair of U-bolts 36, 38 whichextend through a lower bracket 34 and, which in effect clamp the axlehousing to the trailing arm. According to the invention, a supplementalaxle locating member 40 is also held in position by the U-bolts 36, 38.In particular, the left outboard end of the axle housing 41 (shown inphantom in FIG. 8) sits on a saddle 42 which in turn rests on thetrailing arm 10. In the preferred embodiment, a dowel pin (not shown)extends downwardly from the saddle 42 and engages a hole (not shown)formed in the trailing arm 10. The dowel pin serves to help locate theaxle on the trailing arm and resists relative movement between thetrailing arm 10 and the axle 41.

[0032] As seen best in FIGS. 3 and 3A, the supplemental axle locatingdevice 40 includes an axle engaging portion 40 a which rests atop theaxle housing 41 and a shark fin or finger-like extension 40 b (shown inFIGS. 3 and 3A), which extends upwardly and in a slightly forwarddirection. The finger 40 b is engageable with a catcher bracket 44 whichis secured to the side of the frame member 16. In the preferredembodiment, the supplemental locating member 40 is made from castaluminum to reduce weight and includes cavities or recesses such as 48 aand 48 b, to also reduce weight. The finger-like extension 40 b is alsopreferably tapered. The axle engaging portion 40 a also includessemicircular grooves 49 which receive the upper portions of the U-bolts36, 38.

[0033] The finger-like extension 40 b is angled forwardly since the axlehousing in normal operation moves in an arc defined by the trailing arm10. The catcher bracket 44 includes front and rear abutments 44 a, 44 bwhich are engageable with fore and aft surfaces 50 a, 50 b, respectivelyof the finger 40 b. In operation, should a failure in the trailing arm10 occur between its forward mounting and the axle mounting, the catcherbracket 44 will inhibit fore and aft movement of the axle housing. Itshould be understood that the air spring 22 and shock 26 will continueto serve their intended purposes and control the vertical motion of theaxle.

[0034] In an alternate embodiment, a longitudinal plate (i.e., parallelto the frame member) may be mounted across the abutments 44 a, 44 bwhich would inhibit the lateral movement of the axle, i.e., movement ina direction orthogonal to the direction of travel of the vehicle of theaxle housing. In addition, a stop (not shown) may be added to the top ofthe extending finger 40 b to inhibit the finger from moving downwardly,out of the catcher bracket 44.

[0035] Returning to FIG. 2, the disclosed suspension includes featureswhich reduce drive line vibration. This is achieved by lowering thepivot axis 19 of the suspension. With prior art designs, lowering thesuspension pivot point normally results in increased costs, reduceU-bolt integrity, lower traction capabilities and reduced rollstability. The disclosed suspension reduces or eliminates thesedisadvantages by utilizing interconnected, laterally compliant hangerbrackets for the trailing arms.

[0036]FIG. 4 illustrates a suspension incorporating this aspect of thepresent invention. The suspension includes a pair of the pivot armhanger brackets 14 secured to respective frame members 16, 18. Eachhanger bracket is defined by a pair of plates 60, 62, preferably steelplates, which are laterally compliant. In prior art designs, thetrailing arm brackets are typically cast and have very little, if any,elasticity. The hanger brackets 14 extend downwardly and are dimensionedsuch that the pivot axis 19 for the suspension is lowered as compared tomore conventional systems.

[0037] Referring also to FIG. 5, the inner plate 60 of each hanger 14extends downwardly from the associated frame member and is planar.Referring to FIGS. 6 and 6A, the outboard plate 62 includes an upperportion 62 a that is secured directly to and abuts the inboard plate 60.The outboard plate 62 is bent outwardly to define a gap G (shown in FIG.4) at its lower end for receiving the forward end of the trailing arm10. Due to the illustrated configuration, a bending moment M isgenerated in each hanger bracket 14 when loaded tending to bend eachhanger bracket outwardly. The level of the bending moment M is equal tothe load F multiplied by the moment arm L shown in FIG. 4.

[0038] According to the invention, the hanger brackets areinterconnected by a moment canceling member 68. The canceling member 68resists outward bending of the hanger brackets 14.

[0039]FIGS. 2, 5, 6, and 6A illustrate details of the preferredembodiment of this aspect of the invention. The planar inner plate 60 isbest shown in FIG. 5. As seen in FIG. 5, the inner plate includes amounting portion 60 a having a plurality of mounting holes 70 by whichthe plate 60 is secured to the side of the frame member 16. The innerplate 60 includes a generally triangular portion 60 b which extendsdownwardly from its mounting portion 60 a. An oblong hole 72 is locatednear the bottom of the plate 60.

[0040] Referring in particular to FIGS. 6 and 6A, the outboard plate 62,in side view, is similar in shape to the inner plate 60 and includes amounting portion 62 a having a plurality of holes 74 by which the plate62 is secured to the plate 60 and frame member 16. A triangular portion62 b extends downwardly from the mounting portion 62 a. As seen in FIG.6A, the outboard plate 62 is not planar. The triangular shaped portion62 b is bent outwardly and then downwardly to define a mounting section78 of the plate 62, which is parallel to the inner plate 60. In thepreferred embodiment, an oblong mounting hole 80 is formed in theoutboard plate and is aligned with the oblong hole 72 in the inner plate60 when the inner and outer plates 60, 62 are mounted to the frame 16.In the preferred embodiment, the lower mounting section 78 of theoutboard plate 62 is bent along a line 79 that passes through the centerof its oblong hole 80. In addition, an outwardly protruding boss 86 isformed in the outboard plate 62 to strengthen the mounting and toprovide clearance for various trailing arm components to be described.

[0041] Referring also to FIG. 7, the mounting of the forward end of thetrailing arm 10 is illustrated. In particular, the trailing arm includesa circular mount 10 a which receives an elastomeric bushing 90. Athroughbolt 94 extends through the oblong hole 72 in the inner bracketplate 60, through the trailing arm bushing 90 and through the oblongmounting hole 80 of the outboard plate 62. The axial position of thetrailing arm mount 10 a within the bracket 14 is determined by fixedspacers 96, 98 located on either side of the trailing arm and which abutthe trailing arm bushing 90. As seen best in FIG. 7, the outwardlyextending protrusion or boss 86 of the outboard hanger plate 62 providesclearance for the upper part of the trailing arm mount 10 a and itsassociated bushing 90.

[0042] The mounting holes 72, 80 in the inner and outer plates 60, 62,respectively are preferably oblong in order to provide a means foradjusting the longitudinal position of the axle with respect to theframe 16. As seen in FIG. 6, the outboard plate 62 includes alignedholes 102, 104 that are located above and below the oblong mounting hole80. Referring also to FIG. 2, a trailing arm adjustment plate 108 isused to adjust the position of the trailing arm pivot mount 10 a withrespect to its associated bracket 14. In particular, the plate 108includes two holes 102 a, 104 a vertically aligned with a center hole105 (shown in FIG. 10). The center hole is sized to receive the mountingbolt 94 and, when installed in position, is aligned with the oblong hole80 in the hanger bracket 14. The lower hole 102 a is alignable with thelower hole 102 of the hanger bracket plate 62 and is sized such that abolt can be placed through the holes 102 a, 102 and, in effect, definesa pivot for the adjustment plate 108. The upper hole 104 a is sized toreceive a pry bar, lever or other suitable tool through which the upperhole 104 of the outboard plate 62 can be engaged. The pry bar or otherlever-type tool can be used to move the upper part of the adjustmentplate 108 fore and aft to move the pivot bolt 94 (and hence the pivotaxis 19) of the trailing arm fore and aft within the aligned slots 72,80 in the hanger bracket 14. Movement of the pivot axis 19 is used toadjust the final position of the axle with respect to the frame of thevehicle. After the adjustment is made, the mounting bolt 94 is locked inposition (using nut 94 a) in order to lock the position of the trailingarm pivot 10 a.

[0043] As indicated above, the hanger brackets 14 are interconnected bya moment canceling member 68 in order to cancel out or reduce outwardbending movement of the hangers 14. In the preferred and illustratedembodiment, the moment canceling member is at least one wire element 68a (see FIG. 2) that extends between mounting blocks 112 that are securedto the inner bracket plates 60 by respective securing bolts 94.

[0044] In a more preferred embodiment, a pair of wires 68 a is utilizedto provide some redundancy should a failure in one of the wires occur.For a Class 8 truck suspension, piano wire 8 mm in diameter can be used.Referring also to FIG. 7, ends of the wires 68 a are held in themounting blocks 112 which include apertures 113 (shown in FIG. 10). Themounting blocks 112 are held to the sides of the inner plates 60 by thetrailing arm mounting bolt 94 which also extends through the aperture113 of the associated block 112. According to a feature of theinvention, relative rotation between the mounting block 112 and itsassociated inside hanger plate 60 is inhibited by wire extensions 114(shown in FIG. 4) which extend beyond the mounting block 112 and areengageable with a bottom edge of the inside mounting plate 60.

[0045] According to a further aspect of this feature of the invention,the bores 96 a, 98 a, 113 (see FIG. 10) of the spacers 96, 98 andmounting block 112, respectively, are sized to closely fit the mountingbolt 94. By maintaining a close fit between the bolt 94 and the bores ofthese components, the mounting for the trailing arm can better supportlongitudinal loads without causing shifting in the bolt 94 with respectto the hanger brackets 14. As explained above, the plates 60, 62 whichcomprise the hanger bracket, each include an oblong slot (72, 80,respectively) through which the bolt 94 extends. The purpose of theoblong slot is to allow longitudinal adjustment of the trailing arms,thereby providing precise positioning of the axle to which the arms areattached. It is important that the axle be square with respect to theframe in order to minimize tire wear which has been a problem in thetruck industry.

[0046] Once the bolt 94 has been secured by the nut 94 a, relativemovement between the bolt 94 and the plate 60 is resisted by theclamping force on the plate 60 generated between the block 112 and theinboard side of the spacer 96, so long as the bolt 94 cannot move sideto side within the bores of these components. In effect, by closelyfitting the bores 113, 94 a of these components to the bolt size,frictional contact between the block 112 and the inboard side of theplate 60, as well as the frictional contact between the outboard side ofthe plate 60 and the inboard side of the spacer 96 are used to resistrelative movement between the bolt 94 and the plate 60.

[0047] Similarly, the bores 94 a, 105 in the spacer 94, and theadjustment plate 108, respectively, are also sized to closely fit thebolt 94. In this way, the frictional force generated by the clamping ofthe plate 62 between the spacer 98 and the adjustment plate 108 resistsrelative movement between the bolt 94 and the plate 62.

[0048]FIGS. 10 and 11 illustrate another feature of this aspect of theinvention. As indicated above, the bores 96 a, 98 a in the spacers 96,98, the mounting block 112 and the adjustment plate 104 are sized toclosely fit the securement bolt 94. Although the bushing 90 forming partof the trailing arm mount 10 a can also include a bore sized to closelyfit the bolt 94, in the preferred embodiment the arrangement shown inFIGS. 10 and 11 is used to constrict relative movement between the bolt94 and the bushing 90.

[0049] Referring in particular to FIGS. 10 and 11, the spacer 96includes a lip 96 b and the spacer 98 includes a lip 98 b. The outsidediameter of the lips 96 b, 98 b are sized to tightly fit within a bore90 a formed in the trailing arm bushing 90. The lips 96 b, 98 b securethe bushing 90 to the spacers 96, 98 and substantially resist relativemovement between the trailing arm bushing 90 and the spacers 96, 98.Since the spacers 96, 98 have bores that closely fit the bolt 94,relative movement between the bolt 94 and the trailing arm bushing 90 issubstantially resisted. This arrangement assures frictional couplingbetween the plates 60, 62 and their adjacent mounting components, whileat the same time providing a mounting for the trailing arm that resistsrelative movement between the trailing arm mount 10 a and the bolt 94.This is achieved without requiring that the bore 90 a of the trailingarm bushing 90 be sized to closely fit the bolt 94, which would makeassembly of the components more difficult.

[0050]FIG. 11 illustrates the position of the spacers 96, 98 withrespect to the bushing 90 after the bolt 94 is torqued to its finalposition by the nut 94 a. As seen in FIG. 11, the lips 96 b, 98 b areforced into the bore 90 a of the bushing 90, such that the sides of thebushing 90 a are tightly clamped between the spacers 96, 98.

[0051] As far as dimensions are concerned, in a Class 8 truck, a boltwith a diameter of approximately 20 mm has been found to functionsatisfactorily in this application. In order to facilitate assembly, thebore 113 of the spacer 112 and the spacer 96 are sized as 20.2 mm,whereas the bore for the spacer 98 and adjustment plate 108 are sized as20.1 mm.

[0052] To further facilitate assembly, the bolt has various diametersalong its shank. In particular, a section of the bolt indicated by thereference character 180 preferably has a diameter of 20.2 mm. The nextadjacent section indicated by the reference character 182 has a diameterof 20 mm. The next adjacent section indicated by the reference character184 has a diameter of 20.1 mm. The final section of the bolt indicatedby the reference character 186 has a diameter of 20 mm.

[0053] When the disclosed suspension is adapted for use on a Class 8truck, significant lowering of the pivot axis for the trailing arms 10can be achieved resulting in substantially improved suspensionperformance. In particular, in a prior art suspension for a Class 8truck, the distance between the bottom of the frame rail 16 and thetrailing arm pivot axis is typically around 100 mm. Depending on tiresize, the distance between the pivot axis and ground level in aconventional truck will be 500 mm to 600 mm. With the use of “taller”hanger brackets 14 constructed and used in accordance with the presentinvention, the distance between the bottom of the frame member 16 andthe pivot axis 19 can be increased to at least 300 mm and possibly 400mm. This results in a pivot axis to ground dimension (again, dependingon tire size) to be in the neighborhood of 300 mm to 400 mm. Thissubstantial lowering of the trailing arm pivot axis 19 substantiallyimproves performance of the suspension. It should be understood that thepresent suspension can be adapted to other types of vehicles to achievesimilar performance improvements.

[0054] Referring now to FIGS. 2 and 8, another aspect of the inventionis illustrated. Prior art truck air suspensions typically include abridge (not shown) which is attached to the trailing ends of the leftand right trailing arms. This prior art bridge includes seats for theair springs which are typically mounted a substantial distance inboardof the axle ends, due to space restrictions. The positioning of the airsprings inboard of the trailing arms produces moment forces on thetrailing arms tending to generate bending stresses due to twisting ofthe arms.

[0055] According to the invention, the air springs 22 are connected tothe trailing ends of their associated trailing arm 10 by the spring seat21 (shown best in FIG. 8) which is attached to the trailing end 20 ofthe trailing arm 10 by a pair of bolts 142. It should be noted, that thebolts 142 also secure the shock bracket 24 to the trailing arm. As seenbest in FIG. 8, the centerline of the air spring (indicated by thereference character 144) is but a short distance inboard of the trailingarm 10 and, hence, twisting of the trailing arm is substantiallydecreased.

[0056] It should also be noted that the mounting location for the airspring takes advantage of the clearance provided by the inside peripheryof the truck wheel W. Referring also to FIG. 2, the top of the airspring is attached to the frame rail 16 by a bracket 148. In thepreferred embodiment, the centerline 144 of the air spring 22 is locatedat the frame sheer center of the frame rail 16. For a Class 8 truck ofthe type described, the frame sheer center is approximately 15 mm to theoutside of the frame rail. By locating the air spring in the mannerdescribed, torsion forces and twisting of the frame rail is reducedwhich can reduce the strength requirement for the frame rail crossmembers resulting in less weight and lower cost.

[0057] According to a further aspect of this invention, a smaller airspring can be used that is operated at a higher pressure.

[0058] According to still another feature of the invention, the shockbracket 24 includes protection for the lower part of the shock 26. Morespecifically, the bracket 24 includes a pair of ears 24 a (shown best inFIG. 8) which extend beyond the periphery of the shock 26. Should thevehicle be backed into an obstruction, the ears 24 a will contact theobstruction and absorb the initial impact. The bracket 24 is designed toabsorb the shock of-the impact and will bend to absorb the impactforces, thus reducing the possibility of damage to the shock.

[0059] Referring now to FIGS. 2, 3 and 3A, another feature of theinvention is illustrated. To facilitate assembly of the trucksuspension, the supplemental locating member 40 can be used to lock theposition of the suspension with respect to the frame members 16, 18. Inparticular, and as shown in FIG. 2, a bar 154, preferably square incross-section, can be used to lock the finger 40 b to the catcherbracket 44 which is mounted to the frame rail 16. In particular, theabutments 44 a, 44 b each include a hole 155 complementally-shaped tothe bar 154. In the preferred embodiment, the holes in the abutments arealso square in cross-section. The finger 40 b, as best shown in FIGS. 3and 3A, includes a transverse hole 156 also square in cross-section.During initial assembly, the hole in the finger 40 b is aligned with theholes 155 in the abutments 44 a, 44 b and the locking bar 154 is thenpushed through the holes in the abutments and the finger 40 b. Thislocks the position of the suspension and inhibits relative movementbetween the axle 41 and the frame members 16, 18 during the assemblyprocess, thus facilitating assembly. During assembly of prior artsuspensions the suspension cushions are usually filled with air tosupport the axle. This feature of the invention may make the filling ofthe air cushions unnecessary or if the cushions are filled, theirpressurization does not produce any movement in the axle with respect tothe frame because of the locking bar 154. Once the assembly of thevehicle is complete, the bars are easily removed to release the axle andallow relative movement between the axle and the frame.

[0060] For assembly of some trucks, it is common to assemble thesuspension to the frame members, with the vehicle turned upside-down.After completion of the assembly, the frame must be overturned. Thelocking members 154 facilitate this operation. Moreover, in prior artvehicles the air springs have to be filled with air prior to enginestarting, since the air supply is provided by an engine driven pump. Thefeature which allows the suspension to be locked with the locking bars154 eliminates the need for prefilling of the air springs prior toengine start-up.

[0061]FIG. 9 illustrates another aspect of the invention. It is typicalfor highway trucks having air suspensions to provide an automatic heightcontrol. In the past, a height control valve was mounted at thecenterline of the vehicle and included an operating rod connected to theaxle. In recent years, it has been found desirable to have the heightcontrol valve connected to the leading axle in a tandem axle truck, sothat the height of the frame with respect to the leading axle iscontrolled. In trucks in which both axles are driven, it has been foundthat the height control valve cannot be connected to a center point onthe leading drive axle due to the presence of the inter-axle driveshaft. As a result in more recent years, the height control valve hasbeen moved outboard with respect to the centerline of the vehicle. As aresult, it has been found that height control of the vehicle cannot beas precisely maintained as it could when the valve was mounted centrallyin the vehicle. In particular, it was found that a small but perceptibleerror in height control could occur when the vehicle was rounding acurve.

[0062]FIG. 9 illustrates a height control arrangement in which errors inheight control when rounding a curve are eliminated or substantiallyreduced. In particular, a height control valve 170 is mounted to theframe member 16. An operating arm 170 a extends laterally from theheight control valve 170. A height control rod 172 is pivotallyconnected to the distal end of the operating lever 170 a of the heightcontrol valve 170 and extends downwardly in an angled orientation, andis connected to the rear suspension. In the illustrated embodiment, amounting bracket 176 extends from the shock mount bracket 24. The lowerend of the height control rod 172 is connected to this bracket.

[0063]FIG. 9 also indicates the roll center 180 of the vehicle. As canbe seen in FIG. 9, the height control rod 172 generally points towardsthe roll center of the vehicle.

[0064] By positioning the axis 172 a of the height control rod 172 sothat it passes through or closely adjacent the roll center 180 of thevehicle, the roll of the vehicle body that occurs when rounding a curvewill not substantially affect the position of the operating lever 170 aof the height control valve 170. As a result, the valve 170 will notoperate to either admit or release air from the air springs 22 while thevehicle rounds a curve. The illustrated configuration provides theadvantages of a centrally mounted air valve, operated by linkageconnected to the center of the axle.

[0065] It should be noted here that the suspension features describedabove can be used together or separately. For example, the inventioncontemplates use of the supplemental axle locating feature for use withother types of suspensions, including suspensions using trailing armscomprised of multiple leaves, or even conventional leaf suspensions thatdo not employ trailing arms. Similarly, the suspension locking featurecan be used with the illustrated suspension or with more conventionalsuspensions to which the supplemental locating member is adapted.

[0066] The use of compliant hanger brackets which allow lowering of thetrailing arm pivot can be used with or without the supplemental axlelocating member and with or without the height control configuration.

[0067] Although the invention has been described with a certain degreeof particularity, it should be noted that those skilled in the art canmake various changes to it with departing from the spirit or scope ofthe invention as hereinafter claimed.

We claim:
 1. A suspension assembly, comprising: a) a trailing arm; b) ahanger bracket for attaching a leading end of said trailing arm to avehicle frame member and defining a pivot axis for said trailing arm; c)a spring acting between a spring seat attached to said trailing arm andsaid frame member; d) an axle attached to said trailing arm; and, e) asupplemental axle locating member for supplementally locating said axlewith respect to said frame.
 2. The apparatus of claim 1 , wherein saidsupplemental locating member includes a finger-like extension engageablewith a receiving member mounted to said frame.
 3. The apparatus of claim2 , wherein said receiving bracket includes abutment surfaces slidablyengageable with said extension.
 4. The apparatus of claim 3 , whereinsaid supplemental axle locating member is secured to said axle.
 5. Asuspension assembly, comprising: a) a pair of spaced apart trailingarms; b) a hanger bracket associated with each trailing arm andoperative to mount a leading end of said trailing arm to an associatedframe member; c) each bracket comprising a pair of plates having upperends attached to said frame and having lower portions spaced apart fromeach other to define a gap defining a mounting location for said leadingend of said trailing arm; d) said plates being compliant in order toallow controlled bending movement in the bracket; and, e) a momentcanceling member interconnecting said spaced apart hanger brackets forsubstantially canceling outward bending moments of said brackets.
 6. Thesuspension of claim 5 , wherein said inner plate is substantially planarand extends downwardly from said frame in a plane substantially parallelwith said frame member, and said outer plate is bent outwardly and thendownwardly to define a planar section parallel to the plane of saidinner plate.
 7. The apparatus of claim 6 , wherein said inner plate andsaid planar section of said outer plate define aligned mounting holesfor an associated trailing arm, said holes allowing longitudinaladjustment of said trailing arm to precisely locate an axle attached tosaid trailing arm, with respect to said frame members.
 8. The suspensionof claim 7 , further including an adjustment mechanism associated witheach hanger bracket for facilitating adjustment of the position of thetrailing arm with respect to its associated hanger bracket.
 9. Thesuspension of claim 8 , further including spacers for locating saidtorque arm within said gap and sized to provide clamping forces to saidinner and outer plates, whereby relative movement between said trailingarm relative to said hanger bracket is substantially resisted.
 10. Thesuspension of claim 5 , wherein said moment canceling member comprisesat least one wire element extending between the inner plates ofrespective hanger brackets.
 11. The suspension of claim 2 , wherein saidreceiving member and said finger-like extension are adapted toconcurrently receive a locking tool such that relative movement betweensaid axle and said frame member is substantially resisted.
 12. Thesuspension of claim 11 , further including a shock bracket extendingrearwardly from an end of said trailing arm and adapted to pivotallyconnect to one end of a shock.
 13. The suspension of claim 12 , whereinsaid shock bracket further includes abutments that extend beyond aperiphery of said shock and are adapted to receive impact forces wherebypotential damage to said shock is reduced.
 14. The apparatus of claim 1, wherein said spring is located with respect to said frame member, suchthat a centerline of said spring is substantially aligned with a framesheer center of said frame member.
 15. A suspension assembly,comprising: a) a pneumatic spring for resiliently coupling an axle to aframe member; b) a valve for controlling pressurization of saidpneumatic spring, said valve including a control lever; c) an operatingrod for said control valve having one end pivotally connected to saidcontrol lever and another end coupled to said axle, such that movementin said axle produces movement in said operating rods; and, d) saidoperating rod configured and positioned such that an axis of said rodextends through or in close proximity to a roll center of said vehicle.16. The suspension assembly of claim 15 , further including a shock fordamping movements in said axle and including a mounting member to whichsaid other end of said operating rod is connected.